Nuclear Quadrupole Relaxation and Chemical Shift ofXe131in Liquid and Solid Xenon

The spin-lattice relaxation time and temperature-dependent chemical shift of ${\mathrm{Xe}}^{131}$ in liquid and solid xenon have been measured between 9 and 250°K. A calculation of the transition probabilities for quadrupolar relaxation of ${\mathrm{Xe}}^{131}$ in solid xenon via the Raman process is described. The calculation is based on the theory of Van Kranendonk, modified for the case of a face-centered cubic lattice with electric-field gradients arising from exchange and van der Waals interactions. The data are shown to verify the predicted temperature dependence of $T_1$ in the solid above 9°K and the absolute magnitude of $T_1$ at 100°K. It is demonstrated that the temperature dependence of the data is consistent with the temperature variation of the Debye temperature $\Theta$ obtained by Packard and Swenson from specific-heat measurements. Quadrupolar relaxation via diffusing impurities was observed at temperatures near the melting point in solid xenon samples containing roughly 1% air. The quadrupolar relaxation time of ${\mathrm{Xe}}^{131}$ in liquid xenon was found to vary exponentially with temperature with an "activation energy" $E_A=640\mathrm{}\pm 30$ cal/mole. This "activation energy" is approximately one-half as large as values previously obtained for the activation energy of self-diffusion in liquid xenon. Measurements of the chemical shift of ${\mathrm{Xe}}^{131}$ indicate that the local field increases linearly with density in liquid and solid xenon. Least-squares fits to the data yield the change $\Delta H$ of the external resonant field with density: $-\left(\frac{1}{H_0}\right)\left[\frac{\partial \left(\Delta H\right)}{\partial \rho }\right]=(5.1\mathrm{}\pm 0.5)\times {10}^{-7\mathrm{}}$ ${\mathrm{}\left(\mathrm{amagat}\right)\mathrm{}}^{-1\mathrm{}}$ in liquid xenon and $-\left(\frac{1}{H_0}\right)\left[\frac{\partial \left(\Delta H\right)}{\partial \rho }\right]=(18.2\mathrm{}\pm 1.1)\times {10}^{-7\mathrm{}}$ ${\mathrm{}\left(\mathrm{amagat}\right)\mathrm{}}^{-1\mathrm{}}$ in solid xenon. These data support the previous ${\mathrm{Xe}}^{129}$ shift data of Yen and Norberg but disagree with more recent measurements by Brinkmann and Carr of the density dependence of the ${\mathrm{Xe}}^{129}$ shift in solid xenon.